Kim Anderson, an environmental toxicology professor at Oregon State University, told the Los Angeles Times she found a 40-fold increase in polycyclic aromatic hydrocarbons off the Louisiana coast from May to June.

“It’s an incredibly huge jump in concentration in a natural environment,” she said.

Anderson’s team started testing weeks after the April 20 well blowout, taking water samples at four locations near the shore. Results from early August, after the well was capped and stopped leaking, continued to show elevated levels.

The amount of PAHs in crude oil varies, as does the toxicity of the compounds, which constitute a large class of chemicals. Some are carcinogenic, some are not and some are not toxic, Anderson said. Her samples included PAHs of all three types.

Lisa Faust of the Louisiana Department of Health and Hospitals said state testing of seafood harvest areas had not detected harmful levels of the pollutant, the Times reported Friday.